Investigation of the Performance and Micro-Evolution Mechanism of Low-Content Thermosetting Epoxy Asphalt Binder Towards Sustainable Highway and Bridge Decks Paving

The reduction of epoxy resin (EP) content in the thermosetting epoxy asphalt binder can contribute to decrease the cost and carbon emissions, whilst promoting the diversification of their application scenarios. In this study, the performance and microstructure of low-content thermosetting epoxy asphalt (LTEA) binders with EP contents between 30 wt% and 40 wt% were investigated through macroscopic and microscopic methods, and the mechanism of strength formation was simultaneously explained. Moreover, the curing degree of the LTEA binder and the mixture were investigated by Fourier transform infrared spectroscopy (FTIR) and the Marshall test, respectively, and their correlation was established. The results revealed that the mechanical strength of the LTEA binder was enhanced by increasing the EP content, and the LTEA36 binder had good tensile properties. The crosssectional morphology and microscopic phase distribution of the LTEA binder changed significantly when the EP content increased. The phase transition occurred within the LTEA34 binder, which formed a cross-linked network with EP as the continuous phase. The curing degree of the LTEA binder for 24 h was higher than 75%, which corresponded favorably to the curing degree of the mixture. In general, the curing degree of the binder can be used to identify whether the strength of the pavement mixture has reached the specification and reduce the damage to the completed pavement. Additionally, compared to the epoxy asphalt binder with 50 wt% EP content, the cost and carbon emissions of the LTEA36 binder were reduced by 24.8% and 26.3%, respectively. The LTEA36 binder has excellent potential to become a sustainable pavement material for high-grade highways and concrete bridge decks.